A wood substitute is disclosed in Romanian Patent 37832, which consists of a mixture composed of 500 kg/m.sup.3 rice chaff with or without mass addition of wood and, 70-80 kg/m.sup.3 technical urea, the ratio refering to the rice chaff volume.
The product is prepared by the following steps: the ricechaff is artificially dried to 2% humidity and then non-diluted viscous Urelit C as adhesive is added as well as, ammonium sulphate as accelerator and technical urea as inhibitor and then all the ingredients are mixed in a stirrer, in order to obtain a complete homogenizing. Then the homogeneous mixture is poured as a sheet with 60-80 mm thickness and pressed with a pressing force of between 2-6 kg/cm.sup.2 for 15-25 minutes at a temperature between 130.degree.-150.degree. C. in order to finish the polymerization process.
The product and the method to obtain it suffer from the disadvantages of difficult preparation and a limited field of use; the product cannot be moulded in forms in order to obtain finished products.
In accordance with the French Patent 2578187 there is another wood substitute and process to prepare same which has in its composition, resinbark and leaves held together with a mineral binder which assures exclusively the cohesion, in order to obtain this product. The bark is ground or crushed at varied dimensions, then contacted with a mineral binder and a quantity of water which represents the difference between the necessary water quantity for a good setting of the bark used in the process. The mixture of bark, mineral binder and water is obtained through the aid of mechanic equipment then drained before the setting or pressed to obtain plates or panels.
The used mineral binders can be construction plasters, stencil plasters or hydraulic binders such as Portland cement.
This product also suffers the disadvantage of limited physical and mechanical characteristics and a restricted field of use.
Also the Romanian Patent 9262 makes reference to a wood substitute constituted of sawdust or splinters or a mixture of both these materials, with a possible addition of a fibrous material, preferably peat, which are mixed with approximately 3-10% setting material which consists of albumin, preferably bloodalbumin, limestone and soluble glass to which is added a necessary water quatity, then the mixture is pressed at a pressure of over 100 atmospheres, at a temperature of 110.degree. C. In order to obtain the wood substitute, in accordance with this patent, approximately 450 kg sawdust or splinters are mixed with 12-20 kg bloodalbumin, 3-6 kg limestone, 3-6 kg soluble glass and 30-40 kg water, the obtained mixture being pressed at 140-150 atm a temperature of 110.degree. C. into flat forms.
This product suffers from the disadvantage of limited physical and mechanical properties, the impossibility to be moulded in profiled forms in order to obtain final products and the required use of a setting material such as bloodalbumin which is a shortcoming affecting the product.